Apparatus for preventing voids in free-standing piles



W. E. SAXE Dec. 20, 1960 APPARATUS FOR PREVENTING VOIDS IN FREE-STANDING PILES Filed Feb. 24, 1958 2 Sheecs-Sheei'l 1 /NVENTo/e.

WHLTi/ E nxi @WIK .El its Jllli BY H/` HTTOENEYJ. HHRQ/s, K/ECH, FOSTER HP1/ems Dec. 2o, 1960 w. E. SAXE 2,965,248

APPARATUS FOR PREVENTING VOIDS lIN FREE-STANDING PILES Filed Feb. 24, 1958 2 Sheets-Shea?. 2

BY H/S HTTORNEYS. Hee/afs, K/ecH, FosTE/e & Hake/5 APPARATUS FOR PREVENTING VOIDS 1N FREE-STANDIN G PILES Walter E. Saxe, Los Angeles, Calif., assignor to The Conveyor Company, Los Angeles, Calif., a corporation of California Filed Feb. 24, 1958, Ser. No. 717,186

6 Claims. (Cl. 214-10) The present invention relates in general to the prevention or elimination of voids in free-standing piles of owable materials which tend to form as the result of the removal of material from the piles.

For convenience of disclosure, the present invention will be considered herein as applied to a free-standing storage pile of sand utilized in the making of concrete in construction projects. However, it will be understood that the invention is equally applicable to free-standing piles of other ilowable materials.

In many operations requiring large quantities of concrete, such as dam or highway construction projects, it is conventional to set up a concrete mixing plant at the construction site. The sand utilized in the concrete is customarily stored in a large, freestanding, gravitationally-formed pile to which additional sand may be delivered continuously or intermittently in any suitable manner, as by a conveyor leading from a screening apparatus, or other sand source. Such a storage pile is generally substantially conical in shape.

Sand is removed from the storage pile for delivery to the concrete mixing plant by a conveyor means of any suitable type. For example, such conveyor means may include a screw conveyor having its inner end within the pile near the bottom of the pile and adjacent the center thereof. Thus, the conveyor means removes material from within the pile for use in the concrete mixing plant, or for other purposes.

As sand is removed from within the pile, voids frequently form which tend to interfere with the flow of material to the inner end of the conveyor means, due to the fact that the sand is sufciently cohesive to prevent the continuous collapse of the sand into the voids, or is rendered sufliciently cohesive to prevent such collapse by adhesive contaminants in the sand, such as clay, or similar materials. Such voids may take various forms, examples being arches, chimneys, and the like, and they frequently result in complete interruption of the ow of sand to the inner end of the conveyor means.

Since, in large construction projects, storage piles fifty feet or more in height may be necessary to insure an adequate sand supply, the prevention or elimination of such voids presents diicult problems. One conventional procedure which is utilized at the present time to prevent or eliminate such voids is to employ a bulldozer on the pile to lill up chimneys and break down arches. This procedure, while generally satisfactory, is extremely expensive,rparticularly if the pile is so large that several bulldozers must be utilized and/or if around-the-clock operation of the concrete mixing plant requires three shifts of bulldozer operators. Under such conditions, bulldozer costs for preventing or eliminating voids in a sand storage pile utilized in conjunction with a construction project, such as a dam construction project, which may require two or three years to complete may amount to several hundred thousand dollars.

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Another conventional procedure is to tunnel into the sand pile and place therein explosive charges which break up the voids. This procedure, while effective, is expensive and dangerous and cannot be utilized in congested areas, especially since the voids must be eliminated at very frequent intervals.

A primary object of the present invention is to provide a method of and apparatus for preventing or eliminating voids which are elective, yet relatively inexpensive and safe to use, thereby avoiding the aforementioned disadvantages of prior practices.

More particularly, a primary object of the invention is to suddenly discharge a relatively large volume of compressed air at a relatively high pressure within the storage pile adjacent the inner or inlet end of the conveyor means. Such sudden discharge of compressed air produces, in effect, an explosion which elfectively and safely collapses any arches, chimneys, or the like, which may exist, this being an important feature of the invention.

Another object is to provide an apparatus which includes one or more conduits within the pile through which the compressed air may be discharged into the pile, each such conduit having a discharge end within the pile adjacent and above the inner end of the conveyor means and each communicating with a source of compressed air located externally of the pile.

Preferably, the compressed air source is an accumulator adjacent the pile to which the conduit or conduits are connected, each conduit being large so that a large volume of compressed air may be discharged therethrough almost instantaneously.

The accumulator may be charged with compressed air supplied by an air compressor located some distance away from the accumulator for convenience. Since it is necessary to discharge compressed air within the pile only periodically to break up voids, or to prevent their formation, the air compressor may be of relatively small capacity and may be connected to the accumulator by a small air line or pipe. Thus, this construction eliminates any necessity for the provision of a large air compressor and a large air line leading from the compressor.

Another and important object of the invention is to provide means for automatically discharging the accumulator into the storage pile through the conduit mentioned whenever voids form which interfere with theow of material to the inlet end of the conveyor means.

More particularly, an object is to provide a conveyor scale in the path of the material removed from the pile by the conveyor means, and to provide means actuable by the conveyor scale for opening an outlet valve means associated with the accumulator whenever the void or voids in the pile interfere with the flow of material to the inlet end of the conveyor means sulliciently to reduce the weight of material on the conveyor scale below a predetermined minimum.

Another object is to provide a hopper within the pile above the inlet end of the conveyor means, and to provide a void eliminating means comprising a plurality of air conduits having their discharge ends spaced around the periphery of and located above the hopper. Thus,

whenever air is discharged through such conduits, the

formed, generally conical, sand storage pile which may 'be created and maintained in any suitable manner, as by discharging sand thereonto with a suitable conveyor, not

'shown. Within and extending to the exterior of the pile is a tunnel 11, this tunnel extending at least to the `Vcenter of the pile and being shown as extending all the Sand is removed from the pile 10 -by a conveyor means 12 which extends through the tunnel 11 and which is provided with an inlet end 13 disposed adjacent the center of the pile.

way through the pile.

In the particular construction illustrated the conveyor means 12 includes 'a screw conveyor 14.

Sand from the pile 10 is delivered to the inlet end 13 of the screw conveyor 14 of the conveyor means 12 vthrough a downwardly converging hopper 15 mounted on `top of the tunnel 11 and communicating with the inlet end of the screw conveyor through an opening 16 in the tunnel.

Extending into the pile 10 is a main supply conduit 17 connected at its inner end to a header or manifold 18 "which encircles the hopper 15. Communicating with the manifold 18 are discharge conduits 19 having discharge ends 20 spaced around the upper periphery of the hopper 15 and located outwardly of and slightly Vabove the hopper. The outer end of the supply conduit 17 is connected through a quick-opening valve or yvalve means 22 to an accumulator 24. The latter is provided with compressed air by a relatively small aircomy pressor 26 which may be located a considerable dfstance from the accumulator and which may be connected thereto by an air line or pipe 28, the latter being small as compared to the supply conduit 17.

The hopper 15 is provided externally'thereof with a `plurality of manifolds 30 which communicate with the interior of the hopper through downwardly and inwardly inclined holes 32 in the Walls of the hopper. The manifolds 30 are supplied with air through pipes34 which y are shown as connected to a header or manifold 36 encircling the hopper, this header or manifold being shown as being connected to the accumulator 24 by a pipe 38 controlled by a manual valve 40. With this construction, by leaving the valve 40 open, air may be supplied to the sand in the hopper 15 continuously to aeratesame so that it will ow freely into the inlet-end 13 of the d screw conveyor 14, the downward inclination of the holes 32 preventing stoppage thereof by the sand. However, it will be understood that the manifold 36 may be sup- `plied with air for aerating the sand within the hopper 1S intermittently, if desired.

In the construction illustrated, the conveyor means 12 includes a belt-type conveyor section 42 which forms part of a conveyor scale 44 and onto which the outlet end of the screw conveyor 14 discharges. The conveyor section 42 is suspended from a pivoted arm 45 connected -to another pivoted arm 46. Connected to the arm '46 is a counterweighting means 47, which may be a spring means, and which closes a switch 48 whenever the' weight 'on theconveyor section 42 falls below 'a predetermined minimum, indicating interference with the flow of sand -to the inlet end of the screw conveyor 14 by a void 4"within the pile 10, such as a chimneyy 49. The switch 48 :is connected in series with a solenoid 50 for opening the cubicl feet of air.

force of in excess of 4,000 tons with a relatively small valve 22, the connection between the valve 22 and the solenoid 50 being shown diagrammatically by the line 51.

Considering the operationV of the invention, the sand within the hopper 15 is aerated continuously, or intermittently, to keep it free-owing, through the valve 40, the pipe 38, the manifold 36, the pipes 34, the manifolds 30 and the holes 32 leading from the manifolds 30 into the hopper. Whenever a void, such as the chimney 49, of suicient size forms above the hopper 15, the ow of sand through the hopper to the inlet end 13 of the screw conveyor 14 is interrupted, or at least reduced. Almost immediately, this reduction in or interruption of the tlow to the inlet end 13 of the screw conveyor 14 results in a reduction in the amount of sand on the conveyor section 42, whereupon the switch 48 is closed to energize the solenoid 50, which opens the valve 22.

Opening of the valve results in discharging the `accumulator 24 into the pile 10 at a plurality of points around and slightly above the top of the hopper 15. The

supply conduit 17, the header 18 and the discharge conduits 19 are suiiiciently large that the accumulator is discharged almost instantaneously, i.e., within a second vor two. This creates explosions within the storage pile v10 adjacent the chimney 49, or other void, which may interfere with the flow of sand into the hopper 15, the explosions resulting in collapsing of the sides of the chimney into the hopper. It will be noted that the discharge ends 20 of the conduits 19 are directed horizontally toward and encircle any chimney or arch which may form above the hopper 15. Consequently, the explosions produced within the pile 10 upon discharging of the accumulator 24 immediately collapse the sides of the void into the hopper to restore the desired ow of sand. Upon such collapse of the sides of the void, the sand tends to fall into the void approximately along the lines .52, the slopes of these lines depending upon the angle of repose of the material.

In addition to exerting inward forces, the explosions Lresulting from discharging the accumulator 24 Vthrough the discharge pipes 19 produce very large upward forces which disturb the sand all the way to the top of the Vpile to cause the sand to progress inwardly and downwardly along the lines 52 toward the hopper 15. Considering an example of the explosive effect of the compressed air discharge into the storage pile 10 as a matter of illustration, it will be assumed that the stor- .age capacity of the accumulator 24, the How capacities of the conduit 17, the header 18 and the pipes 19, and the opening time of the valve 22 are such that approximately 300 cubic feet of air at a pressure of pounds per square inch will be discharged into the storage pile 10 almost instantaneously, i.e., in a matter of a second or two. The air discharged into the storage pile 10 from the discharge ends 20 of the conduits 19 in the foregoing manner forms generally horizontal pressure fans or lenses with relatively large horizontal dimensions and relatively small vertical dimensions since the compressed air tends to fan out generally horizontally from the discharge ends of the conduits 19. For example, such pressure lenses may have a total horizontal area of 600 square feet and a vertical thickness of 6 inches as a result of the introduction of 300 This results in a momentary upward lateral force, such an upward force being sufficient to break up any voids which may exist. Viewed from another angle, since the air'is discharged into the storage pile 10 at a pressure of 100 pounds per square inch vinthe example mentioned, an upward force of 14,400

pounds will be applied to each column of sand having an `area of one square foot. Since, in a pile of sand -60 feet high, the maximum weight of a column of sand having. an area of one square foot is 6,000 pounds, an upward force of 14,400 pounds is available to lift such 6,000 pound column. As will be apparent, this will resuit in collapsing of any voids which may be present.

The present invention may also be utilized in connection with piles which are not actually being employed as sources of sand, or other materials, but which are left standing as storage piles for prolonged periods to percolate liquid therethrough, such as water for washing purposes. In this case, the shear zones along the angle of repose tend to become impregnated with clay, or other impervious matter, so as to prevent proper percolation. By discharging compressed air into such storage piles periodically in accordance with the present invention, new material will be displaced into the positions occupied by the impregnated material so as to reestablish proper percolation.

An important feature of the present invention is that, by explosively collapsing arches, chimneys, and the like with compressed air only when necessary, minimum quantities of air are introduced into the storage pile. This avoids excessive aeration of the material, which is an important feature.

Thus, the present invention provides an effective, inexpensive and safe way of preventing or eliminating voids in free-standing storage piles. Although an exemplary embodiment of the invention has been disclosed, it will be understood that various changes, modifications, and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claims which follow.

I claim:

l. In an apparatus for producing substantially continuous ow of material from a free-standing storage pile of such material, the combination of: means for removing material from within said pile including conveyor means having an inner end within said pile and an outer end externally thereof; a conduit extending into said pile and having an inner end within said pile adjacent said inner end of said conveyor means and an outer end externally of said pile; an accumulator connected to said outer end of said conduit; an air compressor connected to said accumulator; valve means forI discharging said accumulator through said conduit into said pile to eliminate any voids formed as the result of removal of material from said pile by said conveyor means and interfering with the ilow of material to said inner end of said conveyor means; and means for automatically opening said valve means whenever voids interfering with the flow of material to said inner end of said conveyor means are formed.

2. In an apparatus for producing substantially continuous ow of material from a free-standing storage pile of such material, the combination of: means for removing material from within said pile including conveyor means having an inner end within said pile and an outer end externally thereof; a conduit extending into said pile and having an inner end within said pile adjacent said inner end of said conveyor means and an outer end externally of said pile; an accumulator connected to said outer end of said conduit; an air compressor connected to said accumulator; valve means for discharging said accumulator through said conduit into said pile to eliminate any voids formed as the result of removal of material from said pile by said conveyor means and interfering with the flow of material to said inner end of said conveyor means; and means for automatically opening said valve means whenever voids interfering with the ow of material to said inner end of said conveyor means are formed, including a conveyor scale in the path of material removed from said pile by said conveyor means, and including means actuable by said conveyor scale for moving said valve means to open position.

3. In combination: a freestanding storage pile of material; means for removing material from within said pile including conveyor means having an inner end within said pile and an outer end externally thereof; a conduit extending into said pile and having an inner end within said pile adjacent said inner end of said conveyor means and an outer end externally of said pile; an accumulator connected to said outer end of said conduit; an air compressor connected to said accumulator; valve means for discharging said accumulator through said conduit into said pile to eliminate any voids formed as the result of removal of material from said pile by said conveyor means and tending to interfere with the flow of material to said inner end of said conveyor means; and means for opening said valve means whenever voids are formed which interfere with the flow of material to said inner end of said conveyor means, in-

cluding a conveyor scale inthe path of material removed from said pile by said conveyor means, and including means actuable by said conveyor scale for moving said valve means to open position.

4. In combination: a free-standing pile of owable material; a hopper within said pile; conveyor means within and extending to the exterior of said pile and having an inlet end below said hopper; and means for periodically discharging compressed air into said pile adjacent and externally of said hopper, said air discharging means including a plurality of air discharging elements spaced around the periphery of said hopper and located outwardly of and slightly above said hopper and facing inwardly toward said hopper.

5. In combination: free-standing pile of owable material; a hopper within said pile; conveyor means within and extending to the exterior of said pile and having an inlet end below said hopper; means for periodically discharging compressed air into said pile adjacent and eX- ternally of said hopper; and means responsive to a reduction in the amount of material conveyed by said conveyor means for actuating said air discharging means.

6. In combination: a free-standing pile of flowable material; a hopper within said pile; conveyor means within and extending to the exterior of said pile and having an inlet end below said hopper; means for periodically discharging compressed air .into said pile adjacent and externally of said hopper; and means for aerating the material Within said hopper.

References Cited in the le of this patent UNITED STATES PATENTS 825,532 Green Iuly 10, 1906 1,029,273 Butler .lune 11, 1912 2,304,827 Jewell Dec. 15, 1942 2,367,775 Hohman Ian. 23, 1945 

